Re: PIC Programming - a where to start...

[Pete Shew <pslists@xxxxxxxxx>]

Wayne,
the reason I chose another PIC for the tone generation was that it
was more time critical and I already had quite a lot of stuff in the
interrupt routine for the main PIC, plus I was running out of IO pins,
plus I did some development work to see how to do it on a standalone
PIC, plus I had a 16F84 spare. Of course, I then had to work out how to
tell the tone driver what to generate.

What I found interesting was that for multiple frequency tones, e.g. the
UK dial tone (350Hz + 400Hz), I started with two output bits and a
simple resistive ladder, but the scope showed that only three levels
were present. So I switched to a simple voltage divider with a single
pin as 0v 5v or tri-state to give the three levels. This 1.5 bit DAC
produces very acceptable MF telephone tones. I ended up with four
independent tone generators.

Pete
> Cool!
> I think it may be a while before I'm anywhere close to doing that sort
> of thing though :)
>
> At what point do you choose to use another pic to do a job rather than
> getting a 'bigger and better' main pic and add the task to 'its' list
of
> things its doing?
> (I'm thinking where you said that you were using another pic to do
tone
> generation with your pbx.)
>
> Cheery!
> Wayne
>
>